ASTM A309 – Standard Test Method for Weight and Composition of Coating on Terne Sheet by the Triple-Spot Test (Withdrawn 2015)
Significance and Use
3.1 A coating of terne metal on iron or steel articles is intended to provide drawability, solderability, or corrosion resistance, or combination thereof, which can require different amounts of coating. Specifications for terne-coated sheets frequently provide for these different classes (weights) of coating so that purchasers can select that most suitable for their needs. This test method provides a means of determining the weight of coating for comparison with the material specification requirements.
Note 1—Procedure B (Electrolytic Stripping) and Procedure C (Stripping with Silver Nitrate Solution), formerly in this test method, were discontinued because lack of usage. The designation for Procedure D and Procedure E are retained to avoid future confusion when reference is made only to the procedure designation.
1.2 If the percent of tin in the coating is required, stripping with hydrobromic acid-bromine is the preferred procedure. Steel with a predeposited electrolytic nickel coating requires a two-stage stripping method to determine total tin content. If both the tin and lead percentage are required, stripping with sulfuric acid is recommended, but caution is advised since the sulfuric acid procedure has been found to produce high tin results (see Section 11).